Progress 09/15/03 to 09/14/08
Outputs
OUTPUTS: Objective 4. A major accomplishment this year was completion of two educational manuals for farmers. The first manual, "A Transition Guide to Organic Crop Management" explains what is involved in organic crop production and how to transition. It covers USDA's Organic Standards related to crop production, handling and processing. Each guideline is stated and then followed by a rationale and examples from both scientific information and farmer experience of how the guideline can be met. These manuals have been used in two "Organic 101" workshops held with the Ohio Ecological Food and Farming Association in Ohio and in professional development venues with agricultural consultants. Our "Organic Whole Farm Planning Workbook" uses Holistic Management as a goal setting and planning framework, and guides the user through developing a transition plan and a completed organic farm plan for organic certification. Both manuals are being distributed to farmers, extension personnel and numerous other agricultural professionals in Ohio and across the US. Objectives 2 and 3. We conducted a series of greenhouse experiments to determine the feasibility of niche differentiation to improve soybean competitiveness with weeds. Because of their relative compact growth form, soybeans are more susceptible to fast-growing weeds than is corn. Although they share many niche dimensions with weeds, as legumes, soybeans show clear niche differentiation along one dimension, that of soil N utilization. In our first experiment, we placed soils from organic and conventional farms in greenhouse pots, determined the levels of NO3- present, and added enough wheat straw to the pots to create a C:NO3 ratio of 25 or 50. The pots were planted with one soybean plant, three common broadleaf weeds, and three grass weeds. Additional pots of each soil type received no straw and either contained only a soybean plant (weed-free positive control) or a soybean and the six weeds (negative control) and shoot biomass was determined for each species. Species differences in nutritional niches were suggested first by comparison of growth in the unamended conventional and organic soils. For example, while pigweed grew better in conventional soil, velvetleaf and crabgrass grew better in soil from the organically managed farm. Differences were also evident in response to C amendment. Shoot biomass was reduced for most weed species by C addition, but soybean biomass and bean yield increased. Soybean yield more than doubled with C:N 50 and was not different from yield in pots with no weeds. Pigweed was most dramatically affected by increasing C:N, as most plants died shortly after the cotyledon stage with C:NO3 50. The practical feasibility of this mineral niche differentiation approach was tested by applying high C amendments to certified organic OARDC field plots to change soil C:N: sugar or wheat straw to achieve C:NO3 50 or oak sawdust for C:NO3 50 or C:NO3 75. Greenhouse results were confirmed on the field scale; weed biomass was reduced at elevated C:NO3, while soybean yield was ca. 30% higher in C:NO3 50 plots receiving either sugar or straw and 40-50% higher in plots receiving sawdust. PARTICIPANTS: Partner organizations included the Ohio Ecological Food and Farm Association (OEFFA), Innovative Farmers of Ohio (IFO) and Organic Crop Improvement Association (OCIA) Ohio Chapter 2. These are the leading organic and sustainable farming organizations in Ohio. Three of our Whole Farm Planning Workshops were done in conjunction with IFO. Individual members of these organizations were key stakeholders, serving as advisors to the project and as on-farm research collaborators. These farmers included: Dean McIvaine, (OEFFA); Steve Elliot (OCIA); Ed Snavely (OEFFA); Charles Eselgroth (OEFFA, IFO); Rex Spray (OEFFA); and Hirzel Farms. In the case of Ed Snavely, we tested a practice he developed on his farm for giant ragweed (Ambrosia trifida) control in an experiment at OARDC and set up an on-farm experiment on his farm. Researchers who participated in this project included: Larry Phelan, Deborah Stinner, the late Ben Stinner, Emy Regnier, John Cardina , Phil Rzewnick, Margaret Huelsman, Kathy Bielek, Don Beam, Chris Nacci, and Dave McCartney. Dr. Rzewnicki left OSU early in the project and Dr. Ben Stinner was tragically killed in Nov. 2004. However, he contributed significantly conceptually. Emy Regnier, a giant ragweed biologist in the OSU Horticulture and Crop Science department, helped design, sample and analyze data from a Giant Ragweed Control Experiment conducted over three years. Dr. Phelan conducted all the greenhouse experiments and two field experiments. John Cardina advised on weed ecology questions. Dr. Deborah Stinner oversaw the overall project, the long-term field experiments, development of the two educational manuals, and conducted the whole farm planning workshops. Dr. Huelsman was contracted to write the "Transition Guide to Certified Organic Crop Management" and "Organic Whole Farm Planning Workbook". Kathy Bielek edited and assisted with the production of both manuals. Don Beam, Chris Nacci and David McCartney assisted with field experiments, including sample collection, processing, and data analyses. Chris Nacci assisted in greenhouse experiments as well. TARGET AUDIENCES: The target audience for this project included existing and transitional organic farmers, conventional farmers thinking about transitioning and new farmers. Feedback from our whole farm planning workshops has been very positive as to how the information provided helped participants think about their whole farm and make decisions that are more sustainable. While we have not solved the considerable problem we and other organic farmers in Ohio are having with giant ragweed (Ambrosia trifida), our studies in this project have added some understanding of factors involved in its prevalence and suggestions for ways to control it. This has been much appreciated by organic farmers. With transitional and conventional farmers, we have stressed how important it is to control giant ragweed from the very beginning so it does not get out of control. Our manuals have been released in the past few months and we do not yet have evaluations on how helpful they have been. However, OSU producing these manuals is helping to raise awareness and legitimacy of organic farming not only in the organic community but also in conventional farming circle. We have received press coverage on these manuals from a broad base of agriculture in Ohio and the Midwest, including mainstream news venues. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Herbicides account for >70% of total pesticide sales. However, their use also produces unintended consequences; they are linked to problems for human health and the environment, and herbicide resistance is on the rise for many aggressive weed species. Organic agriculture disallows synthetic herbicides, but the main alternative, tillage, is labor- and energy-intensive and also has negative environmental consequences. Through a combination of greenhouse and field studies, we have demonstrated how principles from plant ecology can be used to inform agricultural soil management to reduce weed pressures. In hydroponic studies of weed and crop nutrition, we have demonstrated the variation in the mineral requirements of different plant species, suggesting that soil minerals play a role in determining why certain weeds dominate in a field and also opens up the possibility of suppressing weeds by optimizing nutrient management. Secondly, we found that the addition of carbon to the soil can shift the competitive balance of soybeans over competing weeds, resulting in higher soybean yields. The mechanism for the carbon amendments is that by stimulating soil microbes, soil soluble N is moved to the microbial fraction of the soil, depriving fast-growing weed species of this limiting nutrient. We have used these findings to educate organic farmers, as well as those interested in transitioning to organic farming, as to the conditions that create weed problems. The research opens the possibility of ecologically based weed management emphasizing prevention, in which field invasibility to weeds is reduced by optimizing soil fertility levels to selectively enhance crop competitiveness over weeds. When integrated with other cultural controls such as cover crops and field sanitation, farmers might be able to reduce their dependence on chemical intervention or mechanical tillage.
Publications
- No publications reported this period
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Progress 01/01/07 to 12/31/07
Outputs
Objective 1. Seven organic farms were sampled for soil parameters (fraction sand, NH4, NO3, microbial biomass N, % organic matter, and particulate organic matter) and weed (total, broadleaves, grasses) estimates as % of total plant biomass. Pre-harvest time sampling at peak grain mass and @50% leaf drop included stand (#/m2), soybean grain, plant, weed and total plant biomass and visual estimates of % weeds. Stepwise regressions were done for the weed and crop parameters versus plant stand and the soil parameters, and the residuals were compared by farm to evaluate farm effect. Evaluations were repeated adding the Spring weed estimates as predictors for fall parameters. Objective 2. We continued collection of soil organic matter, soil fertility and weed data in three field OSU experiments: 1) the Farming Systems Experiment in NW Ohio at the John Hirzel Sustainable Agriculture Research and Education Site 2) the Buckwheat Giant Ragweed Control Experiment, and 3)the
Forage Crop Experiment. In addition, based on observations and results of the 2006 on-farm research in Objective 1 we conducted two field experiments on OSU certified organic research land that were designed to evaluate the effect of stand and row width of food grade soybeans on weeds. Objective 3. Soils from organic and conventional farms were placed in greenhouse pots. The levels of NO3present were determined and enough wheat straw was added to the pots to create a C:NO3 ration of 25 or 50. The pots were planted with one soybean plant, three common broadleaf weeds,a nd three graminoid weeds. Additional pots of each soil type received no straw and either contained only a soybeam plant (weed-free positive control) or a soybean and the sixe weeds (negative control). Plant growth was monitored throughout the experiment, and at the end, we determined final shoot biomass for each species and soybean yield. The experiment was repeated using the additional treatment of C:NO3 75. Objective
4. Three whole farm planning workshops were conducted using Holistic Management as a planning framework. Further development of a Transition Manaul and Ecological Management Guide was conducted. Objective 3.
Impacts
Objective 1: Samples and data are still being analyzed. However, thus far it appears that findings will be similar to 2006. Objective 2: Giant ragweed is a very serious weed for organic soybean production and may cause considerable economice loss. It also can present significant problems in small grains and corn if dense enough. Data from our Buckwheat Giant Ragweed Experiment suggests that late tillage could be a possible solution along with the presence of buckwheat. Data from our Forage Crop Experiment suggest that compost application (1T/Ac) during hay establishment can lower weed counts in subsequent parts of a field crop rotation. 2006 outcomes for other field experiments are not available. Objective 3: Shoot biomass was inversely related to the level of C addition for most weed species, while soybean biomass and bean yield was positively correlated. The most dramatic effect came with pigweed, as most plants died shortly after the cotyledon stage with C:NO3 50.
The second experiment that included C:NO3 75 showed that the higher ratio did not suppress weed growth further but did have a negative impact on soybean yield. Objective 4. Evaluations from workshop participants have been highly positive as to their value.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Objective 1: Six organic farms were sampled for soil parameters (fraction sand, NH4, NO3, microbial biomass N, % organic matter, and particulate organic matter) and weed estimates (total, broadleaves, grasses) as % of total plant biomass. Pre-harvest time sampling at peak grain mass and @50% leaf drop included stand (#/m2), soybean grain, plant, weed and total plant biomass and visual estimates of % weeds. Stepwise regressions were done for the weed and crop parameters versus plant stand and the soil parameters, and the residuals were compared by farm to evaluate farm effect. Evaluations were repeated adding the Spring weed estimates as predictors for fall parameters. ANOVA showed farm differences for all the parameters tested except for fall grassy weed visual estimate and NH4-N. The residuals were significant for farm effect indicating strong differences in management. Spring weediness was the strongest predictor of fall weeds (positive), followed by crop stand
(inverse). Soil parameters were weak predictors of fall weediness. The results point to the importance of good early season weed control and high planting density to minimize late-season weed pressures. Objective 2: The field experiment from last year manipulating soil C:N was repeated with modifications in a different certified organic soybean field. Before planting to soybeans, 3.3m x 6.7m plots in a randomized block design were treated with: poultry manure compost to achieve C:N 5, sugar for C:N 50, sawdust for C:N 50 or 75, sawdust for C:N 50 plus CaCO3 to achieve Ca:Mg 8:1, interplanted with wheat, or left unamended. Overlaid on these amendment treatments were two planting dates, separated by three weeks. Giant ragweed populations proved to be extremely high, such that early planted areas had to be plowed under midseason. Although giant ragweed plant count was significantly lower in late-planted beans, it remained high within the row even with cultivation. A mid-season weed count
census showed no treatment effect on giant ragweed or giant foxtail, the second most common weed; however, total broadleaves except giant ragweed were significantly less numerous in all high C:N treatments than in control plots. At harvest, there were no treatment effects on giant ragweed or soybean plant biomass or yield. Significant effects were recorded for giant foxtail, which was highest in control plots and lowest in all high C:N and wheat plots. No additional benefit was noted for the high Ca:Mg treatment. The results suggest that carbon amendments might reduce many but not all weed species. The experiment needs to be repeated in a field without giant ragweed. Objective 3: C:N effects on giant ragweed were analyzed in the greenhouse, where plants were grown in soil from organic or conventional farms. Wheat straw was added to pots to achieve C:N 25 and 50, or left unamended (C:N 0). Plants in C:N 50 were significantly smaller than those in either C:N 0 or 25 and plants in
conventional soil were smaller than those in organic soil. The largest differences between soils as recorded by mineral analysis for conventional relative to organic were: P and K 3x higher, Fe 1.6x higher, and Cu 3x lower.
Impacts
Information from this project should assist organic and transitional farmers with agroecosystem management strategies that optimize relationships among soil organic matter, soil fertility, insect pests and weeds. Specifically, our proposed hypothesis of Biological Buffering predicts several benefits from the increase in biologically active soil organic matter, including better mineral balance in crops, lower susceptibility to insects and disease, and greater resilience to environmental stresses. We are now extending the hypothesis to determine how manipulations of soil organic carbon might favorably shift the balance of crop-weed competition while reducing herbicidal inputs and mechanical tillage.
Publications
- No publications reported this period
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Progress 01/01/05 to 12/31/05
Outputs
This project has both fundamental and applied goals, i.e., to elucidate the relationships between soil processes and plant health/community dynamics, while providing practical crop production tools that rely more on biological services than on chemical inputs. The project this year has focused primarily on the effects of soil C:N manipulations in soybean-weed competition. Last years studies of soil C:N effects on weeds were repeated using different soil types and extended to include a wider range of C:N. As before, soil was collected from neighboring organic and conventional farms into pots and randomly assigned to blocks in the greenhouse. Each soil was amended with enough wheat straw to achieve soil C:N 25, a mixture of straw and oak sawdust for C:N 50, or sawdust alone for C:N 75. Pots were then planted with soybeans, three grassy weeds, and three broadleaf weeds. Again, C:N 50 produced the highest soybean yield while suppressing overall weed biomass, with soybean
yield in C:N 50 similar to that in unamended soil without weeds. C:N 75 suppressed weeds even more, but also reduced soybean plant biomass and yield. C:N effects were more pronounced for broadleaves than grass species. Also consistent with our previous study, there was a significant amendment x soil source interaction, with C:N effects being generally greater in conventionally managed soils. Pigweed usually did not develop far beyond the cotyledon stage in C:N 50. To separate C:N effects from possible allelopathic effects of wheat straw, a third greenhouse experiment of similar design was conducted, excepting that the same amount of straw was added to all pots, and soil C:N was manipulated by adding different amounts of inorganic N. Once again, C:N 50 suppressed weeds, indicating that the mechanism was not allelopathy, but was related to carbon and nitrogen cycling. Finally, a field experiment was conducted on a certified organic field in which the effects of both carbon amendment
quantity and quality on soybean-weed interactions were considered. Using a randomized block design, 3.05m x 3.05m plots received one of the following incorporated treatments: sugar to attain C:N 50, wheat straw to attain C:N 50, oak sawdust to attain C:N 50, oak sawdust to attain C:N 75, or no amendment. Additionally, treatment plots received in-row cultivation once in late Spring, while unamended buffer strips between plots received two cultivations (2x tillage). These 2x tillage areas were also sampled for comparison. Weed pressure was very high, but also very patchy in the field, even in untreated areas. Dominant species were green foxtail, velvetleaf, and giant ragweed. C:N effects were similar to those seen in the controlled greenhouse experiments, with high C:N treatments (except sugar) producing less weed biomass and higher yield. Due to the very high variability in weed distribution, the randomized block design showed no significant differences; however, if replicates of each
treatment were reassigned to blocks based on rank of weed level or soybean yield, highly significant differences were measured.
Impacts
Information from this project should assist organic and transitional farmers with agroecosystem management strategies that optimize relationships among soil organic matter, soil fertility, insect pests and weeds. Specifically, our proposed hypothesis of Biological Buffering predicts several benefits from the increase in biologically active soil organic matter, including better mineral balance in crops, lower susceptibility to insects and disease, and greater resilience to environmental stresses. We are now extending the hypothesis to determine how manipulations of soil organic carbon might favorably shift the balance of crop-weed competition while reducing herbicidal inputs and mechanical tillage.
Publications
- 2005/01 TO 2005/12 No publications from this period.
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Progress 01/01/04 to 12/31/04
Outputs
Goal: To evaluate the effects of different C:N ratios and soil types on soybean, weed, and insect performance in the greenhouse. By manipulating this ratio, we hope to maintain a microenvironment where the crop plant is successful vegetatively, reproductively, and biochemically while also suppressing the weed community and insect herbivory. Methods: Collected soils from both an organically managed field and a conventionally managed field and placed them in pots. Three C:N ratios were added to each soil, 0, 25, and 50, one week before planting. Three broadleaf weeds and three grass species were planted around soybean in each pot except for a control, which only contained a soybean plant. Measurements were taken over the course of experiment to monitor differences in plant growth of soybeans and weeds. Mexican bean beetle bioassays were conducted with soybean plants grown in different treatments to compare insect developmental performance. We harvested plants and
measured biomass to determine weed and crop performance in different treatments. Outcomes: Data analysis is not complete for Mexican bean beetle development and for some plant growth parameters. However, soybean plant size was significantly larger with C:N 50 than with either C:N 0 or 25 in both soil types, and were not significantly different from soybeans growing without weeds. Weed growth response to soil C:N 50 varied among species, and even showed differences between soil types, but was generally inversely related to soil C:N. Pigweed grew best in conventional soil with C:N 0, while almost all plants died in both soil types with C:N 50. Velvetleaf grew best in organic soil with C:N 0, but was suppressed by C:N 50 in both soil types. Implications: These results illustrate that crop-weed interactions can be modified by changing the C:N of the soil. When growing soybeans, tying up mineral N with moderate amounts of carbon inhibits weed growth while conserving that N for future
crops.
Impacts
Information from this project should assist organic and transitional farmers with agroecosystem management strategies that optimize relationships among soil organic matter, soil fertility, insect pests and weeds.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
The overall goal of this project is to provide scientific information that will assist organic farmers with agroecosystem management strategies to optimize management of organic matter, biologically based soil fertility, pests and crop health. In previous studies under controlled laboratory conditions, we have shown how crops grown under organic conditions have increased resistance to certain insect pests, related this finding to soil biological and chemical characteristics, and described this process in terms of biological buffering. This concept states that a sustained influx of organic matter provides a resource base for soil biological communities that then regulate the balance of plant available nutrients in ways that optimize between plant growth and quality, and defense against pests. In the proposed project, we are extending this work with the following objectives: 1) Investigate relationships between soil organic matter, soil fertility, insect pests and weed
characteristics on a range of certified and transitional organic farms; 2) Investigate relationships between soil organic matter, soil fertility and pest parameters in replicated organic field experiments that evaluate a combination of management strategies based on soil organic matter and crop rotation pattern; 3)Conduct a series of greenhouse experiments designed to discover the mechanisms underlying the relationships observed in Objectives 1 and 2; and 4) Incorporate ecological principles and management information from Objectives 1, 2 and 3 into whole farm planning workshops and a Whole Farm Planning Guide to Organic Farm Management for certified and transitional organic farmers. Our overall hypothesis in the proposed project is that soil fertility maintained by soil biological communities can simultaneously 1) optimize nutrient requirements for crop growth, 2) create chemical balances within the crops that minimize susceptibility to insect pests, and 3) create soil conditions
that alter the competitive balance towards crops versus weeds. This project began October 2003. To date, we have initiated on-farm sampling of certified organic farms under Objective 1. Using soils collected from these organic farms, we are initiating a series of controlled experiments under Objective 2. No results are available at this time.
Impacts
Information from this project should assist organic and transitional farmers with agroecosystem management strategies that optimize relationships among soil organic matter, soil fertility, insect pests and weeds.
Publications
- No publications reported this period
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